Mod squad

Popular Science - - FEATURES - By Sarah Scoles il­lus­tra­tion by Stu­art Pa­tience

With drought parch­ing the West, seed­ing clouds for snow is more im­por­tant than ever. Could this team of sci­en­tists prove it re­ally works?

THE RE­SEARCHERS HAD AL­READY DONE FOUR FLIGHTS, EAR­LIER in Jan­uary, be­fore they saw the first hints of what they were look­ing for. The crew of me­te­o­rol­o­gists, at­mo­spheric sci­en­tists, and stu­dents had con­verged near Idaho’s Snake River Basin, a horse­shoe-shaped de­pres­sion be­tween ranges of the Rocky Moun­tains that is 125 miles at its widest point. Most of the state’s fa­mous spuds come from this arable land. Each day that the weather was right—clouds con­tain­ing the per­fect amount of su­per-cooled mois­ture at the ideal tem­per­a­ture and al­ti­tude— the team flew up into the fluff, dropped sil­ver io­dide, and watched to see if they were mak­ing more snow than there would’ve been if they’d stayed home and hung on to their sil­ver.

It’s called cloud seed­ing. And peo­ple have been plant­ing lit­tle chem­i­cal seeds into puffy white masses, hop­ing to change the weather, for some 70 years. But af­ter all that time, no one knows for sure how well it ac­tu­ally works: when or even if the prac­tice makes more snow fall, or how. That’s what the team be­hind SNOWIE—an acro­nym for Seeded and Nat­u­ral Oro­graphic Win­ter­time clouds: the Idaho Ex­per­i­ment—had come to find out.

“These ques­tions have been around since it started,” says Bob Rauber, one of SNOWIE’s prin­ci­pal in­ves­ti­ga­tors and a pro­fes­sor of at­mo­spheric science at the Univer­sity of Illi­nois at Ur­banaCham­paign. He has been study­ing the phe­nom­e­non since the ’70s. To­day, even though sci­en­tists have a com­puter model that the­o­ret­i­cally cal­cu­lates for suc­cess, “we don’t know if it’s right be­cause we haven’t been able to val­i­date it,” he says.

The day of that fifth flight, Jan­uary 19, 2017, prin­ci­pal in­ves­ti­ga­tor Jeff French, an as­sis­tant pro­fes­sor of at­mo­spheric science at the Univer­sity of Wy­oming, sat inside a tiny King Air prop plane. The pilot flew to 14,000 feet, then back down a cou­ple thou­sand. The air just above them was around 5 to 14 de­grees Fahren­heit, op­ti­mal for the su­per-cooled liq­uids needed to make snow. The plane’s radar was hum­ming, as were in­stru­ments that col­lected in­for­ma­tion on at­mo­spheric pres­sure, tem­per­a­ture, wa­ter va­por, and wind. The mea­sure­ments poured into a set of com­puter-pro­ces­sor racks packed into the four-seater, mak­ing it look like the inside of a sound booth.

French knew that about 1,000 feet above, a sec­ond air­craft was sow­ing flares of sil­ver io­dide, cylin­ders lined up like fire­work car­tridges be­fore a show starts. These ei­ther smol­dered in place on the plane, leav­ing a trail of par­ti­cles drift­ing down, or sprung from its wings and burned out as grav­ity pulled them down to Earth. But French couldn’t see the other plane. In fact, he couldn’t see much at all. That is the thing about fly­ing inside a cloud. What he could see was a feed from the plane’s radar in real-time, show­ing the cloud’s struc­ture above and be­low him, and he could watch the cloud par­ti­cles’ sizes, shapes, and con­cen­tra­tions change.

Be­low him, unseen, the land rose jagged and tree­less at its high­est points, blan­keted in white. When that frozen snow­pack melts each spring, it flows into the basin be­low, pro­vid­ing Idaho res­i­dents not just with house­hold wa­ter, but also

There’s ac­tu­ally no sci­en­tific con­sen­sus about whether the strat­egy works.

with elec­tric­ity from the hy­dro­elec­tric dams that power much of the state.

The craft above French flew back and forth, leav­ing sil­ver io­dide and, if they were suc­cess­ful, snow drift­ing in zigzags over the moun­tains. His plane then cruised through those plumes, its in­stru­ments able to see what French him­self couldn’t: They could de­tect spikes in re­flec­tiv­ity that meant ice crys­tals were bloom­ing, watch them travel with the weather, and per­haps dis­cern whether snow ac­tu­ally ap­peared where the sil­very chem­i­cals had fallen.

On the ground be­low, radars at two re­mote moun­tain sites scanned for the same mea­sure­ments. Staffed by stu­dents who’d snow­mo­biled up the slopes, these in­stru­ments were the first to see a zigzag sug­gest­ing they were in­deed mak­ing snow.

THERE IS SOME­THING SEDUCTIVE ABOUT THE IDEA OF CON­TROL­LING THE WEATHER. Na­ture has foisted pre­cip­i­ta­tion on hu­mans for­ever, forc­ing us to be wet, iced-over, snowed-in, hail-stung, flooded, parched—what­ever, when­ever. Syn­thetic weather mod­i­fi­ca­tion is the ul­ti­mate state­ment that we are supreme be­ings and can make the world per­form to our needs. Pro­grams de­vel­oped in the 20th cen­tury thus try to mit­i­gate hail, make it rain, curb hur­ri­canes, and in­crease snow­fall.

SNOWIE deals with only the lat­ter. By ne­ces­sity, the team’s at­tempt in­volved moun­tains, which play a role in cre­at­ing and steer­ing pre­cip­i­ta­tion. When air ap­proaches a moun­tain, it rises with the land it­self. (Af­ter all, it can’t blow through rock and dirt.) This air chills as it as­cends, and then con­denses into an “oro­graphic” cloud.

Inside clouds, nat­u­ral snowflake em­bryos of­ten form when ice crys­tals grow on tiny par­ti­cles, like dust or gas or pol­lu­tion. Sci­en­tists call these nu­clei. To make more snow, the think­ing goes, add more nu­clei. Sil­ver-io­dide sprin­kles have be­come the go-to ma­te­rial be­cause when they bump into su­per-cooled liq­uid wa­ter, they re­li­ably make it freeze if the tem­per­a­ture is be­low 21 de­grees Fahren­heit. Ski re­sorts and drought-dry re­gions spend mil­lions send­ing sil­ver into the sky, but there’s ac­tu­ally no sci­en­tific con­sen­sus about whether the strat­egy works.

In 2015, the Co­op­er­a­tive In­sti­tute for Re­search in En­vi­ron­men­tal Sciences—a col­lab­o­ra­tion be­tween the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion and the Univer­sity of Colorado at Boul­der—came the clos­est to a con­clu­sion af­ter eval­u­at­ing a decade of snow-fo­cused pro­grams and re­search in a 148-page re­view. “It is rea­son­able to con­clude that ar­ti­fi­cial en­hance­ment of win­ter snow­pack over moun­tain bar­ri­ers is pos­si­ble,” it stated. But later in the same para­graph the au­thors equiv­o­cated, say­ing: “No rig­or­ous sci­en­tific study…has demon­strated that seed­ing win­ter oro­graphic clouds in­creases snow­fall. As such, the ‘proof ’ the sci­en­tific com­mu­nity has been seek­ing for many decades is still not in hand.”

THE IDEA FOR CLOUD SEED­ING SOLIDIFIED—WHERE ELSE?—IN A FREEZER. SPECIF­I­CALLY, THE freezer of Gen­eral Elec­tric sci­en­tist Vin­cent Schae­fer. Schae­fer had be­come in­ter­ested in ice early, ac­cord­ing to his 1993 obit­u­ary in The New York Times. When he was an ice-skat­ing teenager, he ob­sessed over the struc­ture of snowflakes and de­vised a way to trans­fer their like­nesses to film be­fore they dis­ap­peared. As an adult in the 1940s, he put some dry ice into a freezer and breathed into the cold box. “In­stantly the lit­tle cloud turned into tiny ice crys­tals,” the obit re­ports. Schae­fer took that knowl­edge to the skies of Mas­sachusetts in 1946 and dropped 6 pounds of dry ice from a plane. He watched wa­ter ice form and snow fall be­low the plane. That same year, physi­cist Bernard Von­negut—writer Kurt’s brother—re­al­ized that sil­ver io­dide could also be used to seed clouds. Dry ice had to be dropped inside the cloud to work, but sil­ver io­dide could be sowed out­side the cloud and drift in. Sci­en­tists have pri­mar­ily used the com­pound ever since.

SNOWIE in­ves­ti­ga­tor Rauber worked on some of the big fol­low-on re­search projects that came af­ter Schae­fer and Von­negut’s ef­forts. In Steam­boat Springs, Colorado, he and his Ph.D. ad­viser, Lew Grant, im­preg­nated clouds in an at­tempt to un­der­stand their in­ner churn­ings. It was ba­si­cally like SNOWIE, he says, “but with in­stru­men­ta­tion that was the ’70s and ’80s ver­sion of what we have to­day. We were walk­ing around with Coke-bot­tle glasses.”

Other sci­en­tists con­ducted re­search as well, in states

like Colorado, Mon­tana, and Utah. One of the most con­clu­sive ex­per­i­ments, in Aus­tralia in the aughts, sug­gested that seed­ing could in­crease snow by 14 per­cent. But even those re­sults weren’t de­fin­i­tive. The equip­ment just wasn’t good enough to see what in­ves­ti­ga­tors needed to see.

Be­fore SNOWIE, the last big study was 2005’s state-funded Wy­oming Weather Mod­i­fi­ca­tion Pilot Pro­gram. Af­ter nine years and $13 mil­lion, the fi­nal re­sults weren’t con­clu­sive. While one ex­per­i­ment showed no re­sult from seed­ing, oth­ers sug­gested a pos­si­ble pre­cip­i­ta­tion uptick of 5 to 15 per­cent.

In 2014, Rauber and French, along with Bart Geerts, a pro­fes­sor of at­mo­spheric science at the Univer­sity of Wy­oming, and Katja Friedrich, an as­so­ci­ate pro­fes­sor of at­mo­spheric science from the Univer­sity of Colorado at Boul­der, joined forces with the Idaho Power Com­pany and the Na­tional Cen­ter for At­mo­spheric Re­search and ap­proached the Na­tional Science Foun­da­tion. Col­lec­tively they pos­sessed the brains and the brawn to an­swer all the lin­ger­ing ques­tions about cloud seed­ing, they said. And fi­nally, they had the right glasses: in­stru­ments that were pow­er­ful enough to see it in ac­tion. SNOWIE’s radars can mea­sure clouds with fewer and/or smaller par­ti­cles; they can dis­tin­guish at much higher res­o­lu­tion spa­tially and tem­po­rally; they can use higher fre­quen­cies that are sen­si­tive to smaller par­ti­cles. In gen­eral, says French, they have a “sig­nif­i­cantly im­proved abil­ity to di­rectly mea­sure cloud par­ti­cles.” They would col­lect the same kinds of data they al­ways had, but this time they could see the mi­cro­physics of the sit­u­a­tion.

Idaho Power, which has run a seed­ing pro­gram since 2003 de­spite the sci­en­tific un­cer­tainty, would use its plane to dis­perse the sil­ver io­dide and would run its usual data-col­lec­tion sys­tems. The sci­en­tists would em­ploy in­stru­ment-laden planes and moun­tain­top radar sta­tions. The in­for­ma­tion would be recorded on ma­chines pro­vided by the re­searchers, the Na­tional Cen­ter for At­mo­spheric Re­search, and Idaho Power, and would be pooled later for all of them to an­a­lyze. To­gether, they would eval­u­ate what ac­tu­ally went on inside clouds, and what it meant for thirsty ar­eas, ski re­sorts, and hy­dro­elec­tric plants.

By now, these ques­tions have taken on greater ur­gency. What may have started al­most a cen­tury ago as a will­ful urge to make the weather more con­ve­nient for hu­mans has evolved into a ne­ces­sity to sup­port drought-parched re­gions. The county of Los An­ge­les has funded seed­ing projects in ar­eas that drain into its wa­ter­sheds. Utah, Cal­i­for­nia, and Idaho try to boost the snow­pack that melts and then sup­plies their drink­ing wa­ter and drives their hy­dro­elec­tric dams. Colorado ski re­sorts in Vail, Aspen, and Win­ter Park want more snow to sur­vive their crit­i­cal tourism sea­son. “We’re very, very des­per­ate for wa­ter,” says Friedrich, one of SNOWIE’s prin­ci­pal in­ves­ti­ga­tors. “That’s the bot­tom line. Even if it’s just a lit­tle bit of wa­ter, that helps.”

The sec­ond time the SNOWIE team sub­mit­ted a pro­posal, the Na­tional Science Foun­da­tion agreed to spon­sor the project.

THE GROUP SET UP ITS BASE IN IDAHO FROM JAN­UARY 7 TO MARCH 17, WITH THE RE­SOURCES to do around 20 seed­ing ses­sions. Ev­ery day they would de­ter­mine, via their own weather bal­loons and out­side fore­casts, whether the clouds sat­u­rated with su­per-cooled wa­ter would form at the right tem­per­a­ture and height over the moun­tains.

Josh Aikins, Friedrich’s grad­u­ate stu­dent, was a key mem­ber of the moun­tain radar group. He’d snow­mo­biled only once be­fore, when he was a teenager on va­ca­tion in Ver­mont. But he quickly got the hang of slid­ing up to the Packer John Moun­tain radar site, at 7,000 feet of el­e­va­tion—even when the snow was so new and light that the ma­chine meant to float atop it in­stead sank down and needed to be dug out.

Aikins had fallen in love with snow as a kid when the Bliz­zard of ’96 blan­keted the Mid-At­lantic. The snow drifted into banks that reached over the roof of his fam­ily’s York, Penn­syl­va­nia, home. He grad­u­ated from Penn State with a de­gree in me­te­o­rol­ogy but knew he didn’t want to be a weath­er­man. “I’m a T-shirt and shorts guy,” he says.

When the SNOWIE team de­cided to try for a seed­ing run, Aikins and the other radar-run­ners packed up a week’s worth of food and clothes into the ve­hi­cles; given

“Hon­estly, the first time we saw this, I was giddy,” says Rauber. “I was al­most danc­ing around the room.”

that they were pur­pose­fully driv­ing up the moun­tain dur­ing storms, they never knew how soon they’d be able to get back down. One time the 10-mile ride was so chal­leng­ing, it re­quired seven pro­fes­sional snow­mo­bil­ers to help them out.

Each time they ar­rived at their site—a moun­tain­top with a radar sys­tem atop a big truck and an old camper as their lux­ury ac­com­mo­da­tions—Aikins would fire up the gen­er­a­tor, warm­ing up the radar and the camper. “We had a bunch of com­put­ers that we didn’t want to start up cold,” he says, be­cause some elec­tronic com­po­nents won’t func­tion well in that con­di­tion. They’d stash their clothes and food in the camper and dig out the drift-cov­ered porta-pot­ties.

Then they would scan with the radar and watch what the weather was do­ing. When the seed­ing started, they’d search for changes in re­flec­tiv­ity that sug­gested the elec­tro­mag­netic waves were bounc­ing off an area of newly formed ice par­ti­cles.

Aikins re­mem­bers well the day of the first sig­nal. “We saw these lin­ear bands com­ing through the area,” he says, re­fer­ring to the radar read­out. “It didn’t look nat­u­ral.” He sent an email to the com­mand cen­ter, ask­ing if the planes were out. They were. “We could see the seed­ing in real time. We could see the path of the flares.”

In his public field re­port of that flight, prin­ci­pal in­ves­ti­ga­tor Geerts wrote im­pas­sively of their find­ing: “Pos­si­ble seed­ing sig­na­ture… two bands of higher re­flec­tiv­ity aligned with the seed­ing air­craft, drift­ing with the wind and dis­pers­ing over time.”

Put sim­ply: They got it.

AIKINS AND GEERTS SOUND PRETTY STOIC ABOUT THAT FIRST find­ing, con­sid­er­ing it was ex­actly the gold they’d gone West seek­ing. But that’s prob­a­bly be­cause, as Friedrich says, ev­ery­one was —and still is—sus­pi­cious. They haven’t fully an­a­lyzed the data. Their re­sults haven’t un­der­gone peer re­view and been pub­lished in an aca­demic jour­nal.

But their on­line re­ports note three in­stances where snow for­ma­tion could be linked to their ac­tiv­ity. The sec­ond time, Rauber wrote, “The seed­ing sig­na­tures were un­mis­tak­able and dis­tinct, with the lines mim­ick­ing the seeder flight track.” They started to be­lieve maybe the sig­na­tures weren’t a co­in­ci­dence—and they

wanted more. Soon enough, they were re­warded.

“The re­mark­able thing was not that we saw it,” says Friedrich, “but that we were able to re­peat it mul­ti­ple times.”

Rauber, who’s worked in seed­ing with­out cer­tain re­sults for decades, cops to his ex­cite­ment. “Hon­estly, the first time we saw this, I was giddy,” he says. “I was al­most danc­ing around in the room.” Think of it from “the per­spec­tive of an old cloud seeder,” he im­plores. He la­bored through­out the ’70s and ’80s, try­ing to see a sig­nal those Coke-bot­tle glasses just couldn’t bring into fo­cus. And now it’s like he’d had Lasik surgery.

Of SNOWIE’s data, Derek Blestrud—a me­te­o­rol­o­gist with Idaho Power and pres­i­dent of the North Amer­i­can Weather Mod­i­fi­ca­tion Coun­cil— said, “What we got was well above and be­yond what any­body imag­ined.”

EVEN THOUGH THE TEAM CAP­TURED THOSE ZIGZAGS, THEY STILL HAVE A LOT of work to do be­fore they can tell the world ex­actly how—and how well—cloud seed­ing might work. De­pend­ing on who you ask, they’ll be dig­ging into data for four to six years, although they aim to get the whiz-bang re­sults out within 12 months. “We have more data than any of us ever dreamed of be­ing able to col­lect,” French says.

The plane alone scooped up 25 gi­ga­bytes of data on each of its 18 flights, gleaned from the radar and laser sys­tems, as well as from its di­rect tem­per­a­ture, pres­sure, and wa­ter-va­por probes. The sci­en­tists will sort through that and ground-based re­search, and do some in­ter­pre­ta­tion and anal­y­sis on lo­cal ma­chines at their uni­ver­si­ties and at the Cen­ter for Se­vere Weather Re­search in Boul­der, Colorado. That will give them a rudi­men­tary un­der­stand­ing of what the gi­ga­bytes sig­nify: the physics of how snow forms and falls nat­u­rally in the moun­tains, how burn­ing bits of in­or­gan­ics al­ter them, the im­pact on weather as a whole. As French puts it, they’ll have 100 pieces of a 5,000-piece jig­saw puz­zle.

To get the com­plete pic­ture, they’re gonna need a big­ger box—a su­per­com­puter. The Na­tional Cen­ter for At­mo­spheric Re­search has a new one named Cheyenne, with 5.34 petaflops of ca­pac­ity. It’s the 20th-fastest cal­cu­la­tor on the planet. Cheyenne will show how well the phys­i­cal ob­ser­va­tions—from the planes, the radars, and the real world— match up with the pre­dic­tions. And based on how well they do or don’t, the SNOWIE team and other sci­en­tists can then tweak the pre­dic­tors to bet­ter see which weather is the most fer­tile for mod­i­fi­ca­tion.

This isn’t just about Idaho. SNOWIE will fig­ure out the un­der­ly­ing mech­a­nisms that de­ter­mine how clouds come to form, evolve, and drop snow—whether seeded or not—down to Earth. “It should ap­ply any­where,” says Geerts. Af­ter all, physics is physics, on Earth as it is in heaven, as it is where the two meet.

Sarah Scoles is the au­thor of Mak­ing Con­tact: Jill Tarter and the Search for Ex­trater­res­trial In­tel­li­gence, pub­lished in July by Pe­ga­sus.

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